The present invention relates to the field of charge driver circuits, and in particular, to a bi-directional charge driver circuit.
Various circuits utilize switches in combination with a capacitor. For example, certain switch capacitor circuits are used to provide adjustment circuitry for timing signals, where the charge on the capacitor affects the period, pulse width, delay, or other aspect of the timing signals. Other applications for switch capacitors include regulation circuitry that utilizes the capacitor as a capacitive load to regulate an output signal to a desired level.
The present invention is directed to a bi-directional charge driver circuit that is operable to increase or decrease the charge on a capacitance circuit. The bi-directional charge driver circuit arranged to sink and source current to the capacitance circuit in response to two control signals. The capacitance circuit provides an output voltage that corresponds to the charge stored on the capacitance circuit. In one embodiment, the output voltage corresponds to an adjustable voltage reference that may be increased or decreased as required. In another embodiment, the two control signals are produced according to a logic circuit in response to two digital input signals. In this embodiment, the bi-directional charge driver circuit operates as a digital-to-analog converter, converting the two digital input signals to an analog output voltage. In yet another embodiment, one of the digital input signals is a pulse signal produced by a pulse generator circuit, wherein the pulse signal has an associated pulse width that affects the amount the capacitance circuit is charged and discharged.
Briefly stated, a bi-directional charge driver circuit provides an output voltage that may be increased or decreased according to two control signals. When the output voltage is configured as an adjustable reference voltage, the adjustable reference voltage may be varied in selectable increments to obtain a desired reference voltage. Alternatively, when the bi-directional charge driver circuit is configured as a digital-to-analog converter, the two control signals are given by a logic circuit in response to two digital input signals. The two digital input signals are converted by the bi-directional charge driver circuit to the analog output voltage.